Poiseuille Flow

$v_z(r)=\frac{R^2}{4\eta }\frac{\Delta P}{L}\left(1-\frac{r^2}{R^2}\right)$

• The flow velocity in the direction of the tube
• $R$ is the radius of the tube
• $\eta$ is the viscosity
• $\Delta P$ is the pressure gradient
• $L$ is the length of the tube